Kull Spring07 Lesson 22 Ch 7/8 1 CHAPTER 8 Atomic Electron Configurations and Chemical Periodicity Road Map - Lesson 22 Recap of Ch 7 problems Area of Focus : Chapter 8 The Exclusion Principle introduction of the 4 th q.n. Electron Spin Subshell filling order Atomic electron configuration Kull Spring07 Lesson 22 Ch 7/8 2Equations wavelength x frequency speed of light = wavelength x frequency c = X = 3.00 x 10 8 m/s = nh(c/ ) E = nh = nh(c/ ) n= positive integer Plancks constant(h) = x 10 34 J s E atom = E emitted (or absorbed) radiation = nh Rydberg equation = R n 2 > n 1 R = x 10 7 m -1 E = E final E initial = 2.18 x 1018 J E photon = E state A E state B = h Kull Spring07 Lesson 22 Ch 7/8 3 Quantum mechanics Quantum number Values Total number n shell/level 1,2,3, n = # subshells n 2 = # orbitals in a shell - subshell/ sublevel - subshell/ sublevel 0, 1, n-1 n-1 m - orbital - - , 0, + 2 2 +1 (orbitals in a subshell) m s - spin + , - 2 possible Kull Spring07 Lesson 22 Ch 7/8 4 According to the quantum mechanical treatment of the hydrogen atom, which set of quantum numbers is not allowed? A) n = 3, = 2, m = 0 B) n = 3, = 0, m = 0 C) n = 3, = 1, m = 1 D) n = 3, = 1, m = -1 E) n = 3, = 1, m = 2 Practice Problem 22-1 Kull Spring07 Lesson 22 Ch 7/8 5 According to the quantum mechanical treatment of the hydrogen atom, which set of quantum numbers is not allowed? A) n = 3, = 2, m = 0 B) n = 3, = 0, m = 0 C) n = 3, = 1, m = 1 D) n = 3, = 1, m = -1 E) n = 3, = 1, m = 2 Practice Problem 22-1 Answer Kull Spring07 Lesson 22 Ch 7/8 6 For an excited hydrogen atom with the quantum number n equal to 9, which of the following statements is true? A) The energy of the atom is less than the energy for the state in which n is equal to 8. B) If = 0, there are nine possible values for the magnetic quantum number m . C) The smallest value of the magnetic quantum number m is -9. D) The electron must be in one of the p orbitals. E) The angular momentum quantum number can have any of the values 0, 1, 2, 3, 4, 5, 6, 7, 8. Practice Problem 22-2 Kull Spring07 Lesson 22 Ch 7/8 7 For an excited hydrogen atom with the quantum number n equal to 9, which of the following statements is true? A) The energy of the atom is less than the energy for the state in which n is equal to 8. B) If = 0, there are nine possible values for the magnetic quantum number m . C) The smallest value of the magnetic quantum number m is -9. D) The electron must be in one of the p orbitals. E) The angular momentum quantum number can have any of the values 0, 1, 2, 3, 4, 5, 6, 7, 8. Practice Problem 22-2 Answer Kull Spring07 Lesson 22 Ch 7/8 8 According to the quantum-mechanical model, how many orbitals in a given atom have n = 3? A) 4 B) 7 C) 9 D) 10 E) 18 Practice Problem 22-3 Kull Spring07 Lesson 22 Ch 7/8 9 According to the quantum-mechanical model, how many orbitals in a given atom have n = 3? A) 4 B) 7 C) 9 D) 10 E) 18 Practice Problem 22-3 Answer Kull Spring07 Lesson 22 Ch 7/8 10 Chapter 8 The Exclusion Principle introduction of the 4 th q.n. Hunds rule Electron Spin Subshell filling order Atomic electron configuration Kull Spring07 Lesson 22 Ch 7/8 11 Chapter 8 Pauli Exclusion Principle - No two electrons in the same atom can have the same set of 4 quantum numbers. each electron has a unique address. HUNDS RULE - When placing electrons in a set of orbitals having the same energy, we place them singly as long as possible. aufbau principle is the building up process that results in ground-state electron configurations Kull Spring07 Lesson 22 Ch 7/8 12 Electron Configurations and the Periodic Table Active Figure 8.7 Kull Spring07 Lesson 22 Ch 7/8 13 Electron Filling Order Figure 8.5 Kull Spring07 Lesson 22 Ch 7/8 14 Quantum mechanics Quantum number Values Total number n shell/level 1,2,3, n = # subshells n 2 = # orbitals in a shell - subshell/ sublevel - subshell/ sublevel 0, 1, n-1 n-1 m - orbital - - , 0, + 2 2 +1 (orbitals in a subshell) m s - spin + , - 2 possible Kull Spring07 Lesson 22 Ch 7/8 15 Writing Atomic Electron Configurations Two ways of writing configs. the spdf notation. 2) the orbital box notation. Two ways of writing configs. the spdf notation. 2) the orbital box notation. 1 1 s value of n value of l no. of electrons spdf notation for H, atomic number = 1 One electron has n = 1, l = 0, m l = 0, m s = + 1/2 Other electron has n = 1, l = 0, m l = 0, m s = - 1/2 Kull Spring07 Lesson 22 Ch 7/8 16 PhosphorusPhosphorus All Group 5A elements have [core ] ns 2 np 3 configurations where n is the period number. Group 5A Atomic number = 15 1s 2 2s 2 2p 6 3s 2 3p 3 [Ne] 3s 2 3p 3 Yellow P Red P Kull Spring07 Lesson 22 Ch 7/8 17 Kull Spring07 Lesson 22 Ch 7/8 18 PERIODIC TRENDS Kull Spring07 Lesson 22 Ch 7/8 19 General Periodic Trends Atomic and ionic size # electrons # shells Larger orbitals, -electrons held less tightly Ionization energy Electron affinity energy involved when an atom gains an electron to form an anion. Effective nuclear charge When higher: Electrons held more tightly Kull Spring07 Lesson 22 Ch 7/8 20 Trends in Atomic Size Kull Spring07 Lesson 22 Ch 7/8 21 Effective Nuclear Charge, Z* Z* is the nuclear charge experienced by the outermost electrons. Z* increases across a period owing to incomplete shielding by inner electrons. The 2s electron PENETRATES the region occupied by the 1s electron. 2s electron experiences a higher positive charge than expected. Estimate Z* by --> [ Z - (# inner electrons) ] Charge felt by 2s e- in Li Z* = = 1 Be Z* = = 2 B Z* = = 3and so on! Kull Spring07 Lesson 22 Ch 7/8 22 Ion Configurations To form cations, always remove electrons of highest n value first! P [Ne] 3s 2 3p 3 - 3e- ---> P 3+ [Ne] 3s 2 3p 0 Kull Spring07 Lesson 22 Ch 7/8 23 Ion Sizes CATIONS are SMALLER than the atoms from which they come. The electron/proton attraction has gone UP and so size DECREASES. Li,152 pm 3e and 3p Li +, 78 pm 2e and 3 p + Forming a cation. Kull Spring07 Lesson 22 Ch 7/8 24 Ion Sizes ANIONS are LARGER than the atoms from which they come. The electron/proton attraction has gone DOWN and so size INCREASES. Trends in ion sizes are the same as atom sizes. Forming an anion. F, 71 pm 9e and 9p F -, 133 pm 10 e and 9 p - Kull Spring07 Lesson 22 Ch 7/8 25 Trends in Ion Sizes Active Figure 8.15 Kull Spring07 Lesson 22 Ch 7/8 26 Ionization Energy IE = energy required to remove an electron from an atom in the gas phase. Mg (g) kJ ---> Mg + (g) + e- Mg+ (g) kJ ---> Mg2+ (g) + e- Mg+ has 12 protons and only 11 electrons. Therefore, IE for Mg+ > Mg